Testosterone is considered THE male hormone, standing for aggression and posturing. Researchers around Prof. Dr. Armin Falk, an economist from the University of Bonn, have now been able to demonstrate that this sex hormone surprisingly also fosters social behavior. In play situations, subjects who had received testosterone clearly lied less frequently than individuals who had only received a placebo. The results have just been published in the Public Library of Science's international online journal "PLoS ONE."